Hey guys, I am looking to buy some Hi flow Cats in the near future. I have a question. When you dyno and get a wideband O2 reading the best place to get this from is pre cats right? This would make me think I need some o2 bungs welded onto my new cats. The question is do you put sensors in the bungs that the dyno plugs up to, or do you plug them up and the shop puts in sensors that come with the dyno?

 

Most take one of your sensors out and install theirs for the dyno.

 

FYI , if you buy crawford CATs the best.easiest place to weld in an O2 bung is "Pre-CAT on the Passenger side". The CAT shield needs to be trimmed back a little , but it will fit. Pretty similar story with Kinetix CATS, but with Kinetix there is a little easier since the CAT sits back further from the front flange.

 

Someone at my shop answered it for me. It's best to do the readings pre cat. What you do is have bungs welded onto the cats (right after the header) They uncap the bungs put in their sensors, and take the readings, makes sense to me. How would the car run right if you take out an o2 sensor?

 

Car should run fine, since the tuner would use the "addtional" bung , not the OEM pre-CAT (in header) bung for tuning.
All OEM O2 sensors should remain intact for tuning.

 

I thought he meant they take out a stock sensor(if the bung wasn't present) Do you only need one bung. Would it be better to have two? Is it possible to have two?

 

It is only possible to read one side at a time on the dyno. I recommend doing the bung on the driver side since #6 cylinder is the rear cylinder and usually runs the hottest.

 

Side depends on type of CAT used. I note that the Crawford has more useable room on the pasenger side CAT to place a bung, other CATs are different. Doug recommended the passenger side for that reason, but of corse with the Crwaford plenum there should also not be the leaner cylinder # 6 lean as there is with th OEM plenum.

 

Yes, I did mean take the stock sensor out. Unless you plan on doing a lot of dynos it is not worth the time to have a bung welded in. The reason is the ecu is in open loop and the oxygen sensor is not being read.
The car is in open loop when deceleration, acceleration, high load, high speed, malfunction of o2, low o2 temperature, High engine coolant temps, and when starting.
So running the car on the dyno will not be effected by not having the o2 out or in.

 

Thanks for the info guys.

 

Adding a cockpit WB (aka AEM etc..) meter is reason enough to add the extra O2 bung. Once that bung is there , it is the preferred orfice for tuning. The useful trio of guages for FI is "Boost, Fuel psi, WB A/F" IMO. Also if you track the car, Oil temp is also useful. Wth a WB A/F meter, EGT is not nealry as useful.

 

Hey kyle, do you work for SGP? I am going to have all my dyno work done there when the car is ready.

 

Yes...I work for/own SGP

 

Sorry for the dumb question, I knew that you were the owner, just worded the question wrong. I will take your advice and have it welded on the drivers side. Is there any reason to put one on both sides or would it be a waste of time/ money?